Method of sealing sheet metal boxes



Oct. 31,1950

T. BARON ETAL METHOD OF SEALING SHEET METAL BOXES Filed Nov. 4. 1947 I NVENTORS Theodore Baron Robert Wenbevger BY HIS ATTORNEYS fiatentecl Oct. 31

METHOD OF sperms sIiEEr METAIiB'oxEs 1 Th r aron anditober lll inbergcr. L ndo England, assignors to Carreras Limited, London, England, a British company ApplicationNov mhei' 4, 1947, Serial No. 784g018 In Great Britain May 9, 1940 see-eat 1, ettiiataw 6'91; new; 8'', i946 Patent expires May 9, 1960 y 1. This invention has for its object to provide an improved method and means whereby an airtight and water-tight sealing maybe conveniently and efiicintly effected between" the lid and the body of a tin plate or other metal box without need 'for resorting to soldering;- I

According to this invention the joint between related metal box parts is effectively sealed by applying thereto with the aid of heat and pressure a composite sheet material composed of a strip of tin, aluminiurnor likemetal foil faced orr one side with india rubber, gutta perch'a or like impervious material adapted under the influence of heat to soften and assume an adhesive condition. vA further feature of this invention is the provision of an improved apparatus by meansof which the composite sheet material.

may be prepared and applied to metal boxes requiring to be sealed.

It is possible to apply the rubber in a liquid form on to the foil in the machine as is the case in the application of adhesives, but this is not advisable since rubber solvents are inflammable and dangerous.

Metal foils can be provided with a coating of rubber in a separate working process and the strips wound up into the form of spools which later on can be used in the box sealing machine.

It is, however, better for the gutta-percha and foil to be wound on separate spools and placed in the machine and united in the machine itself and in the same working operation, since in this way a preliminary heating of the length of foil is saved. When the strip of foil provided with the coating is placed in contact with th tin, the strip must be heated, as otherwise the tin will not take this reliably and accurately.

On the annexed drawing is shown diagrammatically 'a tin sealing machine, arranged, according to the invention, for this process.

I is aspoo-l of metal 'foil, 2 the gutta-percha spool, and 3 and 4 the separate strips of these materials which are carried over the drum 5'.

This drum is heated. Therubber strip unites with the metal strip owing to the heat rendering it soft and adhesive.

If only one spool is used, with the rubber combined with the metal foil, the composite material 6 must be carried over th heating body 1.

For the further conveyance of the strip of material into the range of the tin or box [6, the grips or fingers commonly employed in labelling machines cannot be used since the soft viscous gutta-percha would at onc soil and glue up these parts. According to the invention there- 2 Claims. (01. 21 6 -62) fore this e0nveya 'nc is instead effected by ec":

tion devices. The arrangement of the conveyor device shown by way of example,- consists of a chain conveyor I? on which are fitted pairs of small suction cups or holders i0; H. These suction holders" are co'nnecte'd by small tubes or pipes I4" with a band l3 travelling therewith. This band closes an air space which is sub-f divided. The chamber I5 is under vacuum or partial vacuum; When the pair of suction hold; ers come within the range of the length of ma: terial, they also come into communication with ,the chamber under vacuum or partial vacuum and the material is held by suction and carried along. When the strip is in the correct position with respect to the box IE to be sealed, which is moved transversely to the length of material, a cutter 9 which may be of any desired type, comes into operation and cuts this strip 3 from the continuous length of web. In the meantime, the suction holders I0, I I carry the length of material along. The space between the suction holders H! and II as indicated above, must be left for the passage between them of the boxes 16' to be sealed. Naturally the path of the conveyor or chain [2 must be in a plane removed from that in which the suction holders travel, and thus the suction holders mustproject laterally out of the path of the chain 22.

Although the sealing strip is warmed, and the rubber facing is still sticky it is carried along by the suction holders in a reliable manner, re-

sembling that usual with sealing strips coated with gum and used for closing cardboard boxes. The suction holder shown on the left can, like the suction holder shown on the right, communicate either with the chamber under partial vacuum or with the atmosphere. A certain resistance to the pulling of th strip by the box [6 must be offered, in order to ensure that the separated strip contacts securely with the side of the box I6.

On being depressed the box 56 with the attached sealing strip 8 passes down a chute formed between opposed guide members I1, I 8 which consists of heated plates pressed resiliently by springs I9 against the side walls of the box. As the box enters this chute the free portions of the sealing strip are brought into engagement with the sides of the box as shown at I6 and the heating efiect of the plates ll, I8 brings about a vulcanisation of the rubber facings of the sealing strip.

On reaching the end of this chute the box is propelled laterally by a reciprocatin pusher 2| into a, passage formed between opposed guide members 22, 23, also consisting of heated plates adapted to be pressed resiliently against the boxes by springs 24, this passage being directed at right angles to the aboveamentioned chute. Just before the box is moved from one channel way to the other as shown at I6 a reciprocating blade 20 moving parallel with but in advance of the pusher 2i and turns down on to the wall of the box that terminal part of the strip 8 which is toward said pusher 2!. Immediately following this action the box is moved by the pusher 2| into the channel formed between the opposed guides 22, 23, whereupon the remaining terminal part of the foil strip is turned down on to the wall of the box where it also laps over the opposite end of the foil in order to complete the seal as shown at H6 The further movement of the boxes into, from and through the machine may be provided for in any desired way since this forms no part of the present invention.

We are aware that it has previously been proposed to render cigarette and other boxes air proof and moisture proof by adhesively afiixing over the joint between the body of the box and its cover a rip seal consisting of a strip of cellulose derivative or metal foil th inner side of which is coated with glue and carries a strip of lesser width or a cord adapted to assist in tearing the seal strip when it is required to open the box but we make no claim to such arrangement.

We claim:

1. The process for sealing a lid to a metal plate can, which comprises heating a metal strip faced with an elastomer to render said elastomer soft and adhesive, and pressing said heated strip around said can'with said heated elastomer in contact with said lid and said can along their line of union.

2. The process for sealing a lid to a metal plate can, which comprises uniting a metal strip and a strip of elastomer'to form a compound strip, heating said compound strip to render said elastomer soft and adhesive, and pressing said heated compound strip around said can with said elastomer in contact with said lid and said can along their line of union.

THEODORE BARON. ROBERT WEINBERGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

